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Leaf nitrogen (N) and phosphorus (P) stoichiometry correlates closely to leaf morphology, which is strongly impacted by wind at multiple scales. However, it is not clear how leaf N, P stoichiometry and its relationship to leaf morphology changes with wind load. We determined the leaf N and P concentrations and leaf morphology-including specific leaf area (SLA) and leaf dissection index (LDI)-for eight Quercus species under a simulated wind load for seven months. Leaf N and P concentrations increased significantly under these conditions for Quercus acutissima, Quercus rubra, Quercus texana, and Quercus palustris-which have elliptic leaves-due to their higher N, P requirements and a resultant leaf biomass decrease, which is a tolerance strategy for Quercus species under a wind load. Leaf N:P was relatively stable under wind for all species, which supports stoichiometric homeostasis. Leaf N concentrations showed a positive correlation to SLA, leaf N and P concentrations showed positive correlations to LDI under each wind treatment, and the slope of correlations was not affected by wind, which indicates synchronous variations between leaf stoichiometry and leaf morphology under wind. However, the intercept of correlations was affected by wind, and leaf N and P use efficiency decreased under the wind load, which suggests that the Quercus species changes from "fast investment-return" in the control to "slow investment-return" under windy conditions. These results will be valuable to understanding functional strategies for plants under varying wind loads, especially synchronous variations in leaf traits along a wind gradient.

In order to clarify the relationship of leaf characteristics and growth of Catalpa bungei and provide a theoretical basis for clone selection in Catalpa bungei, the growth and leaf morphology characteristics of 61 Catalpa bungei clones were studied. The results showed that significant variances were found in leaf length, width, width/length, leaf stalk length, specific leaf mass, Diameter at Breast Height (DBH) and height among 61 clones. Leaf length, width and leaf stalk length were positively correlated with each other. Leaf length and leaf stalk length were positively related to DBH and height and leaf width was positively related to height. This suggests that leaf morphological indices, such as leaf length, leaf stalk length and leaf width, can predict the tree growth for Catalpa bungei clones, which would be helpful for clonal selection in future.